Polyvinylamine has been used in many industrial and pharmaceutical applications. In the papermaking industry, polyvinylamine has been used as dry and/or wet strength additives as well as retention/drainage aids. Polyvinylamine has a linear backbone structure with no branches and possesses one primary amine group for every two carbon units. The polymer is highly cationic in an aqueous system with a broad pH range due to the high density of the primary amine. Thus, it has a strong hydrogen bonding ability, suitable for a variety of industrial applications.
Polyvinylamine has typically been made by free radical polymerization of N-vinylformamide monomer followed by a direct base- or acid-catalyzed hydrolysis by which the primary amine is deprotected and formic acid is released. A partially hydrolyzed and water-soluble homopolymer of N-vinylformamide that contains N-vinylformamide units and vinylamine units has also be prepared, as disclosed in U.S. Pat. No. 4,421,602. U.S. Pat. No. 2,721,140 discloses the use of polyvinylamine as an additive to make papers having high wet strength. U.S. Pat. No. 4,421,602 also disclosed the use of polyvinylamine and a 50% hydrolyzed polyvinylformamide to increase efficiencies of flocculation, retention of fines and drainage rate of pulp fiber in papermaking process. U.S. Pat. No. 5,961,782 discloses the use of polyvinylamine to make crosslinkable creping adhesive formulations. U.S. Pat. No. 6,159,340 disclosed the use in papermaking of polyvinylamine and a 50% hydrolyzed polyvinylformamide as dry and wet strength additives in paper and paperboard production. U.S. Pat. Nos. 6,616,807 and 6,797,785 disclose the use of polyvinylamine as drainage aids, flocculants and retention aids in the paper industry. Despite its unique properties and wide applications of polyvinylamine and its derivatives, other polyvinylamine alternatives are still being sought.
As disclosed in U.S. Pat. No. 4,774,285, N-vinylformamide monomer may be copolymerized with an additional vinyl monomer, e.g., vinyl acetate, followed by a subsequent hydrolysis to produce a water-soluble copolymer of vinylamine and vinyl alcohol. These water-soluble copolymers may be used as wet and dry strength additives for papermaking. Further, U.S. Pat. No. 5,630,907 disclosed copolymer compositions containing vinylamine units and acrylic acid units, and their applications. U.S. Pat. No. 6,797,785 disclosed copolymer compositions containing vinylamine units and diallyldimethylammonium (chloride) (“DADMAC”) units or acrylamide units via reverse emulsion polymerization, and the uses of those copolymers as flocculants and coagulants for the papermaking industry. EP 0251182 disclosed a copolymer that contains vinylamine units and acrylonitrile units for use in papermaking as drainage, retention agents, and as a wet end additive to increase dry strength resin of paper products. In general, those copolymer compositions contain vinylamine units and an additional vinyl units linked together randomly through C—C bond in a linear fashion, and those compositions reduce the density of vinylamine units in the polymer backbone, thereby giving it a lower cationic charge density as compared to polyvinylamine.
The derivatization of polyvinylamine by modifying the primary amines is an alternative approach to produce polyvinylamine analogs with altered physical and application properties. For example, U.S. Pat. No. 5,292,441 disclosed the use of quaternized polyvinylamines as flocculants for wastewater clarification and the quaternized polyvinylamines are obtained from the reaction of a polyvinylamine with a quaternizing agent such as methyl chloride, dimethyl sulfate or benzyl chloride. U.S. Pat. No. 5,994,449 disclosed a resin composition that is a reaction product of epihalohydrin with a mixture of a poly(vinylamine-co-vinyl alcohol) copolymer and a polyaminoamide and use of this composition as a creping adhesive.
The present invention is directed to modification of polyvinylamine through a Michael addition reaction. Michael addition is a chemical reaction that involves a conjugate addition of a nucleophile to an α,β-unsaturated bond conjugated to an electron-withdrawing group, particularly α,β-unsaturated carbonyl compounds resulting in a chain-extended product. One interesting advantage of this addition reaction is that there are no by-products released by the reaction. As a result, the Michael addition reaction has been widely used in organic synthesis and also applied to polymer chemistry on many occasions.